"Bert Coules" wrote in message
...
Dave,

You don't need to. Simply make it large enough and slop in a dollop of
quickset mortar. Wedge the box in place until it dries.

And then mark for the securing screw, remove the box and drill and plug
the
hole, you mean? I have tried that in the past with reasonable results;
perhaps I'll give it another go. Thanks.


I tend to drill the securing holes & plug before the dollop of plaster - as
you tighten the screws pullng the box home it squeezes the plaster out & it
can be scraped off flush. All rock solid & secure once it's set.

--
Richard Sampson

mail me at
richard at olifant d-ot co do-t uk